There are many electronic apparatus comprising a piezoelectric crystal resonator made of a piezoelectric material such as quartz crystal. For example, cellular phones, wristwatches, facsimiles, digital cameras, digital TV sets, DVD recorders and i-Pods comprising a quartz crystal resonator are well known. Recently, because of high stability for frequency, miniaturization and the light weight nature of these electronic apparatus, the need for an electronic apparatus comprising a smaller quartz crystal resonator with a frequency of high stability has arisen. For example, the quartz crystal resonator having a quartz crystal tuning fork resonator capable of vibrating in a flexural mode housed in a quartz crystal unit and electrically connected to an amplifier, a plurality of capacitors and resistors is widely used as a time standard in an electronic apparatus such as the cellular phones, the wristwatches, the facsimiles, the digital cameras, the digital TV sets, the DVD recorders and the i-Pods.
Heretofore, however, it has been impossible to obtain an electronic apparatus comprising a miniature piezoelectric crystal tuning fork resonator of the prior art, capable of vibrating in a flexural mode, and having a frequency of high stability, a small series resistance and a high quality factor. This is the reason why, when miniaturized, the piezoelectric crystal tuning fork resonator of the prior art, capable of vibrating in a flexural mode has a smaller electromechanical transformation efficiency. As a result of which, the piezoelectric crystal tuning fork resonator has a frequency of low stability, an increased series resistance and a reduced quality factor.
Simultaneously, there has been a big problem in disposing electrodes on tuning fork tines and a tuning fork base of the miniature piezoelectric crystal tuning fork resonator, such that the electrodes disposed to excite the miniature piezoelectric crystal tuning fork resonator can not be connected well and satisfactorily as required.
Additionally, there has been a big problem in a crystal oscillator having the piezoelectric crystal tuning fork resonator of the prior art, such that an oscillation frequency of a fundamental mode of vibration of the piezoelectric crystal tuning fork resonator which is an output signal of the crystal oscillator jumps to a second overtone mode of vibration thereof by shock or vibration.
It is, therefore, a general object of the present invention to provide embodiments of a piezoelectric crystal tuning fork resonator, a piezoelectric crystal unit having the piezoelectric crystal tuning fork resonator and an electronic apparatus having the piezoelectric crystal tuning fork resonator, which overcome or at least mitigate one or more of the above problems.